Hello all, I ran into an issue where write transfers were randomly failing with "data parity" errors (bit 9 set in ERRSTS). This seems to be caused by a hardware bug, probably the same as v3.12-rc2-5-gbf41691 addresses. The problem appeared on an x86_64 kernel after enabling Xen support (CONFIG_XEN), which appears to be completely unrelated but, as a side effect, changed the alignment of the private structure (struct ismt_priv) allocated at the beginning of ismt_probe(). On x86_64, addresses returned by kmalloc are guaranteed to be only 8-byte aligned. However, i2c-ismt apparently was always getting a 16-byte aligned address. Since the hardware seems to have issues with unaligned DMA buffers (at least in some revisions), I believe it is safer to always align the buffer at the cost of 15 extra bytes of memory. The first patch tackles this. The second patch in the series adds a register dump at the end of transactions (when debugging is enabled). This is not critical, but probably helps debugging issues where some general/master registers are changed as result of a failed transaction. -Radu Radu Rendec (2): i2c: ismt: 16-byte align the DMA buffer address i2c: ismt: dump registers at the end of transactions drivers/i2c/busses/i2c-ismt.c | 39 +++++++++++++++++++++------------------ 1 file changed, 21 insertions(+), 18 deletions(-) -- 2.9.5
